The present invention relates to a method for controlling an engine installed with a continuously variable transmission (hereinafter referred to as CVT), and more particularly to a method for controlling the speed of the engine during a transient shifting period.
A continuously variable transmission having a V-belt extending between driving and driven pulleys, with one or both of the pulleys being able to adjust the size of their respective V-shaped openings which hold the V-belt, thereby controlling the revolution ratio between the driving and driven pulleys. The size of the V-shaped opening is varied by changing the amount of pressure being fed into a hydraulic cylinder of either of the pulleys. Hence, the effective diameter of the pulley can be varied by changing the amount of pressure being fed into the hydraulic cylinder, thereby allowing for a continuously varying ratio of driving pulley effective diameter to driven effective pulley diameter. The V-shaped openings on the driving and driven pulleys are each defined by an area between a fixed portion of the pulley and a movable portion of the pulley, the size of the V-shaped opening being dependent upon the pressure inputted to the hydraulic cylinders. In order to provide hydraulic pressure to each of the movable pulleys, a hydraulic apparatus is provided.
A prior hydraulic apparatus was designed in a manner which provided for the engine rpm to be a function of the amount of throttle opening while maintaining a minimum fuel consumption. When an operator applied a force to an accelerator pedal, the engine speed was immediately increased. This fact generally resulted in an increase in the fuel consumption by the engine during a transient shifting period.